Debinding process for removing an organic binder from a powder compact

Abstract

A process of debinding a powder compact formed from a mixture of a sinterable powder and an organic binder utilizes a furnace for heating therein the powder compact at a pressure lower than an atmospheric pressure in order to remove an excess amount of the organic binder. A control is made to vary the furnace pressure and/or a heating rate in accordance with a monitored parameter so as to effectively and successfully removed an excess amount of the organic binder which would cause an unacceptable defect in a finished product. The parameter is selected as indicative of a condition of the furnace or a cracked gas being generated by decomposition of the organic binder, and includes, for example, a furnace temperature, density, volume, or the other measurable characteristics of the cracked gas.

What is claimed is: 
     
       1. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   monitoring a temperature of a furnace; and   heating said powder compact within said furnace at a pressure lower than an atmospheric pressure, while variably controlling said pressure in accordance with a varying temperature of said furnace, so as to control an amount of cracked gas generated.   
     
     
       2. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   heating said powder compact within a furnace at a pressure lower than an atmospheric pressure;   detecting a variation in density of a particular component of a cracked gas being generated by thermal decomposition of said organic binder; and   controlling to vary a heating rate as well as said furnace pressure in accordance with said density variation.   
     
     
       3. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   heating said powder compact within a furnace at a pressure lower than an atmospheric pressure;   detecting a variation in volume of a particular component of a cracked gas being generated by thermal decomposition of said organic binder; and   controlling to vary a heating rate as well as said furnace pressure in accordance with said volume variation.   
     
     
       4. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising.   heating said powder compact within a furnace at a pressure lower than an atmospheric pressure;   detecting a decrease in weight of said organic binder caused by thermal decomposition thereof;   controlling to vary a heating rate as well as said furnace pressure in accordance with said weight decrease of said organic binder in said powder compact.   
     
     
       5. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   heating said powder compact within a furnace at a pressure lower than an atmospheric pressure;   placing within said furnace a monitor member kept at a temperature below a condensation temperature of said organic binder to be capable of condensing thereat a cracked gas having been generated by thermal decomposition of said organic binder from said powder compact,   directing a light beam or a sound wave to said monitor member to detect transmissibility or reflectance thereof; and   controlling to vary a heating rate as well as said furnace pressure in accordance with the detected transmissibility or reflectance of said monitor member.   
     
     
       6. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   heating said powder compact within a furnace at a pressure lower than an atmospheric pressure;   directing a light beam or a sound wave to a space around said powder compact to detect transmissibility or reflectance thereof; and   controlling to vary a heating rate as well as said furnace pressure in accordance with the detected transmissibility or reflectance of said space.   
     
     
       7. In a debinding process of heating a powder compact shaped from a mixture of a sinterable powder and an organic binder to remove an excess amount of said organic binder from said powder compact, an improvement comprising:   monitoring a temperature of a furnace; and   heating said powder compact with said furnace at a pressure lower than an atmospheric pressure, while variably controlling said pressure in accordance with a varying temperature in such a manner as to lower the pressure to near a vacuum level when the temperature is detected to be within a first temperature range where the degradation reaction is expected to be less intense and therefore less volume of cracked gas being generated and to raise the pressure to near atmospheric pressure level when the temperature is detected to be within a second temperature range where the degradation reaction is expected to become intense to generate correspondingly increased volume of cracked gas.